Finding acceptable coatings for foods, such as fresh fruits and processed and vegetables, cheeses, bakery goods, raw and cooked eggs, fresh and processed meat, and seafood products, is a challenging task. Coatings should be edible and once applied, act as a barrier to moisture, gases and/or UV light, and undesirable microorganisms. However, several other criteria are also important: the coating should be essentially harmless to consumers, transparent (or nearly so) in the visible region so the coated product is visible to the consumer, and it should impart no significant odor or taste to the foods.
In addition, edible coatings and films that offer promise as packaging materials due to one or more functional properties often suffer from poor water resistance (highly water soluble). Satisfying all these criteria simultaneously and satisfactorily has presented a serious challenge to researchers and as yet no suitable solution has been found.
Anthocyanins provide the majority of red, purple, and blue pigmentation of some fruits and vegetables, and their greater consumption has been suggested to mitigate the risk of chronic disease in humans. Unfortunately, these pigments are highly labile and vulnerable to degradation during thermal processing. Further complicating matters is their water-solubility that promotes their leaching into aqueous media. Thus, innovative technologies are needed to overcome long-standing technical barriers experienced by the food industry to retain these health-promoting pigments during food handling and processing.
Fresh produce (fruits and vegetables) and plants in general commonly lose water to their surroundings during production, harvesting, handling and storage. This water loss can cause damage, dieback, and death to plants and plant parts in general, as well as changes in the appearance, texture and quality of the produce, which most consumers find unappealing. This results in decreased marketability, and limits acceptable shelf-life and storage times.
Exposure to high levels of UV light can damage developing and maturing produce creating visibly damaged and discolored tissues, destroying native healthful phytochemical compounds, stimulating production of undesirable and harmful compounds like ethylene gas, and providing a foothold for spoilage organisms to grow. Such produce suffers a loss of perceived quality, reduced health benefits and is generally deemed unsuitable for the fresh market. Further, the phenomenon can potentially ruin a grower economically, as the conditions leading to its occurrence are shared by the entire crop.
Fresh produce damage can be caused by both external and internal influences. External influence is the most common and can be easily seen when fresh produce cracks in the rain. Rainwater is absorbed through the cuticle due to a high osmotic potential (due to the sugar content of fruit) inside the fresh produce. The water moves across the membrane in order to equalize the potential. The produce then swells to the point beyond which the skin can expand and the produce splits open. The internal influence of fruit damage is the buildup of tensile forces within the produce as a result of water uptake through the vascular system within the tree itself. This can be most clearly seen in covered orchards where fruits occasionally split, although protected from the rain.
Previously frozen foods typically exude liquid during thawing, resulting in a phenomenon called “drip loss.” This can be off-putting to consumers, and can change the overall composition of the thawed product, making it behave differently from fresh during preparation/cooking. Drip loss also can cause economic losses to the processors.